Study On The Controllable Synthesisof 2D MoSe₂-based Composite Nanomaterials And Its Electrochemical Properties

With the fastimprovement and advance of human civilization and the enormous use of conventional fossil energies,on the one hand,it causes serious pollution to the environment;on the other hand,the shortage of non-renewable energy also gradually threatens and restricts the development of society.As a result,in order to improve the environment and solve the problem of energy shortage,scientists all over the world are committed to seeking new clean and easily available renewable energy.In recent years,transition metal disulfide compounds have attracted much attention and exploration from researchers due to their high efficiency,cleanness,abundant reserves and special physical and chemical properties.They have been widely used in various fields such as natural,life and science,becoming a class of functional inorganic materials with potential application.Although a large number of experimental studies and reported results have shown the preparation methods and application of transition metal disulfide compounds,it becomes big focus for the researchers that how to optimize the properties of transition metal disufide compounds and realize their controllable synthesis through simple and easily available methods at present.In this work,we aim to use MoSe2 as a typical transition metal disulfide,which application is limited by its poor conductivity and insufficient active sites.It is designed to synthesize MoSe2 with other transition metal disulfide compounds by solvothermal method tosynthesis newly nanocomposite materials with application valueand study the application of these modified MoSe2 nanomaterials in electrocatalytic hydrogen evolution reaction,supercapacitor and oxygen evolution reaction.The keystudyconsequences of this paper include the following:1.A two-step hydrothermal injection method was designed to prepare multi-layer aggregated MoSe2/Co9S8 composite nanomterials,and their electrocatalytic hydrogen evolution and oxygen evolution reaction properties were investigated.In the experimental study,the MoSe2 utra-thin nanosheets were prepared at 240℃ by using oleylamine as solvent,dibenzyldiselenide and molybdenum acetylacetonate as selenium and molybdenum sources in the oil phase system.Then mixed solution with dibenzyldiselenide and cobalt acetylacetonate as sulfur and cobalt sources were injected into the hydrothermal solution,and Co9S8 nanoparticles were grown on the MoSe2 nanosheets.The characterization results of XRD,TEM,XPS and other tests shown that we successfully synthesized MoSe2/Co9S8 composite nanomaterials with uniform dispersion and multi-layer aggregation.Electrochemical tests shown that when the synthesized MoSe2/Co9S8 composite nanomaterial were used as catalysts for electrocatalytic hydrogen evolution(in 0.5 M H2SO4)and oxygen evolution(in 1 M KOH)reactions simultaneously,the overpotential of the composite nanomaterial is significantly reduced to 178 and 343 mV respectively at a current density of 10 mA cm-2 compared with pure phases MoSe2 and Co9S8.These results show that the composite nanomaterial not only improves the conductivity of the MoSe2 nanosheets,but also increases the active edge area.2.A simple and easy-to-operate one-step hydrothermal injection method was developed to realize the controllable preparation of nanoflower-lice MoSe2/NiSe composite nanomaterials.The nanoflower-like MoSe2/NiSe composite nanomaterials were obtained by using oleylamine as a solvent and injecting a mixed solution with nickel acetylacetonate,molybdenum acetylacetonate dioxide and dibenzyldiselenide as precursor sources at 280℃.At the same time,we also studied the effect of different nickel acetylacetonate content on the reaction results.In addition,we applied the as-prepared MoSe2/NiSe nanocomposite to electrocatalytic hydrogen evolution and supercapacitor.The test results show that the composite with 20%nickel acetylacetonate has the best electrochemical performance.When it was used as an electrocatalytic hydrogen evolution catalyst,a current density of 10 mA cm-2 can be achieved at an overpotential of 146 mV.When the electrode material was used as supercapacitor in 3 M KOH solution and the current density is 1 A/g,a higher capacitance of 421.5 F/g can be obtained.